Lyme disease, due to infection with the Ixodes tick-transmitted spirochete Borrelia burgdorferi, is the most common vector-borne disease in the United States, with over 20,000 cases reported to the CDC annually. There is controversy over the length of antibiotic therapy that is necessary to achieve a clinical cure for Lyme disease. Serologic tests (ELISA and immunoblot) that detect antibodies against B. burgdorferi are currently the most sensitive and widely available laboratory tests for Lyme disease, but they do not assess response to therapy and can not distinguish previous exposure to B. burgdorferi from active infection. The determination of when a laboratory cure is achieved after antibiotic treatment remains a large, unmet medical need for distinguishing acute infection or re-infection from previous exposure and for preventing unnecessary treatment with long-term courses of antibiotics. To address this need, we have assessed antibiotic therapy in the mouse model of Lyme borreliosis. We found that IgG responses decline rapidly to a subset of Borrelia antigens after successful antibiotic therapy. This Phase I proposal seeks to improve upon the currently available serologic tests for Lyme disease through a proteomic approach that will a) identify the B. burgdorferi antigens to which murine antibody responses decline after successful antibiotic treatment and b) evaluate their diagnostic potential in distinguishing active infections from those cured with antibiotics. Declines in titer or loss of reactivity to the antigens will be correlated with antibiotic sterilization that will be confirmed by multiple measures. The candidate diagnostic antigens will be produced as recombinant proteins and tested for reactivity with sera from mice treated with antibiotics at different stages of infection and patient sera representative of various stages of B. burgdorferi infection. The specificity and sensitivity of these diagnostic tests in patients will be determined in Phase II, and quantitative ELISA assays that predict successful elimination of infection by antibiotics will be developed for use in commercial clinical laboratories. PUBLIC HEALTH RELEVANCE: Lyme disease is an infection with the tick-transmitted spirochete Borrelia burgdorferi. Some people have lingering symptoms even after antibiotic therapy, and there is no test to determine the effectiveness of antibiotics at eliminating the infection. Our intent is to significantly improve the evaluation of patients treated for Lyme borreliosis through the introduction of new serologic tests that predict when infection has been cured and distinguish prior exposure from active infection.